Patrick Welche <prlw1@cam.ac.uk>

[netbsd-mini2440.git] / external / ibm-public / postfix / dist / src / tls / tls_misc.c

/*      $NetBSD$        */

/*++
/* NAME
/*      tls_misc 3
/* SUMMARY
/*      miscellaneous TLS support routines
/* SYNOPSIS
/*      #define TLS_INTERNAL
/*      #include <tls.h>
/*
/*      char    *var_tls_high_clist;
/*      char    *var_tls_medium_clist;
/*      char    *var_tls_low_clist;
/*      char    *var_tls_export_clist;
/*      char    *var_tls_null_clist;
/*      char    *var_tls_eecdh_strong;
/*      char    *var_tls_eecdh_ultra;
/*      int     var_tls_daemon_rand_bytes;
/*
/*      TLS_APPL_STATE *tls_alloc_app_context(ssl_ctx)
/*      SSL_CTX *ssl_ctx;
/*
/*      void    tls_free_app_context(app_ctx)
/*      void    *app_ctx;
/*
/*      TLS_SESS_STATE *tls_alloc_sess_context(log_level, namaddr)
/*      int     log_level;
/*      const char *namaddr;
/*
/*      void    tls_free_context(TLScontext)
/*      TLS_SESS_STATE *TLScontext;
/*
/*      void    tls_check_version()
/*
/*      long    tls_bug_bits()
/*
/*      void    tls_param_init()
/*
/*      int     tls_protocol_mask(plist)
/*      const char *plist;
/*
/*      int     tls_cipher_grade(name)
/*      const char *name;
/*
/*      const char *str_tls_cipher_grade(grade)
/*      int     grade;
/*
/*      const char *tls_set_ciphers(app_ctx, context, grade, exclusions)
/*      TLS_APPL_STATE *app_ctx;
/*      const char *context;
/*      int     grade;
/*      const char *exclusions;
/*
/*      void    tls_print_errors()
/*
/*      void    tls_info_callback(ssl, where, ret)
/*      const SSL *ssl; /* unused */
/*      int     where;
/*      int     ret;
/*
/*      long    tls_bio_dump_cb(bio, cmd, argp, argi, argl, ret)
/*      BIO     *bio;
/*      int     cmd;
/*      const char *argp;
/*      int     argi;
/*      long    argl; /* unused */
/*      long    ret;
/* DESCRIPTION
/*      This module implements routines that support the TLS client
/*      and server internals.
/*
/*      tls_alloc_app_context() creates an application context that
/*      holds the SSL context for the application and related cached state.
/*
/*      tls_free_app_context() deallocates the application context and its
/*      contents (the application context is stored outside the TLS library).
/*
/*      tls_alloc_sess_context() creates an initialized TLS session context
/*      structure with the specified log mask and peer name[addr].
/*
/*      tls_free_context() destroys a TLScontext structure
/*      together with OpenSSL structures that are attached to it.
/*
/*      tls_check_version() logs a warning when the run-time OpenSSL
/*      library differs in its major, minor or micro number from
/*      the compile-time OpenSSL headers.
/*
/*      tls_bug_bits() returns the bug compatibility mask appropriate
/*      for the run-time library. Some of the bug work-arounds are
/*      not appropriate for some library versions.
/*
/*      tls_param_init() loads main.cf parameters used internally in
/*      TLS library. Any errors are fatal.
/*
/*      tls_protocol_mask() returns a bitmask of excluded protocols, given
/*      a list (plist) of protocols to include or (preceded by a '!') exclude.
/*      If "plist" contains invalid protocol names, TLS_PROTOCOL_INVALID is
/*      returned and no warning is logged.
/*
/*      tls_cipher_grade() converts a case-insensitive cipher grade
/*      name (high, medium, low, export, null) to the corresponding
/*      TLS_CIPHER_ constant.  When the input specifies an unrecognized
/*      grade, tls_cipher_grade() logs no warning, and returns
/*      TLS_CIPHER_NONE.
/*
/*      str_tls_cipher_grade() converts a cipher grade to a name.
/*      When the input specifies an undefined grade, str_tls_cipher_grade()
/*      logs no warning, returns a null pointer.
/*
/*      tls_set_ciphers() generates a cipher list from the specified
/*      grade, minus any ciphers specified via a list of exclusions.
/*      The cipherlist is applied to the supplied SSL context if it
/*      is different from the most recently applied value. The return
/*      value is the cipherlist used and is overwritten upon each call.
/*      When the input is invalid, tls_set_ciphers() logs a warning with
/*      the specified context, and returns a null pointer result.
/*
/*      tls_print_errors() queries the OpenSSL error stack,
/*      logs the error messages, and clears the error stack.
/*
/*      tls_info_callback() is a call-back routine for the
/*      SSL_CTX_set_info_callback() routine. It logs SSL events
/*      to the Postfix logfile.
/*
/*      tls_bio_dump_cb() is a call-back routine for the
/*      BIO_set_callback() routine. It logs SSL content to the
/*      Postfix logfile.
/* LICENSE
/* .ad
/* .fi
/*      This software is free. You can do with it whatever you want.
/*      The original author kindly requests that you acknowledge
/*      the use of his software.
/* AUTHOR(S)
/*      Originally written by:
/*      Lutz Jaenicke
/*      BTU Cottbus
/*      Allgemeine Elektrotechnik
/*      Universitaetsplatz 3-4
/*      D-03044 Cottbus, Germany
/*
/*      Updated by:
/*      Wietse Venema
/*      IBM T.J. Watson Research
/*      P.O. Box 704
/*      Yorktown Heights, NY 10598, USA
/*
/*      Victor Duchovni
/*      Morgan Stanley
/*--*/

/* System library. */

#include <sys_defs.h>
#include <ctype.h>
#include <string.h>

#ifdef USE_TLS

/* Utility library. */

#include <vstream.h>
#include <msg.h>
#include <mymalloc.h>
#include <vstring.h>
#include <stringops.h>
#include <argv.h>

 /*
  * Global library.
  */
#include <mail_params.h>
#include <mail_conf.h>

 /*
  * TLS library.
  */
#define TLS_INTERNAL
#include <tls.h>

 /* Application-specific. */

 /*
  * Tunable parameters.
  */
char   *var_tls_high_clist;
char   *var_tls_medium_clist;
char   *var_tls_low_clist;
char   *var_tls_export_clist;
char   *var_tls_null_clist;
int     var_tls_daemon_rand_bytes;
char   *var_tls_eecdh_strong;
char   *var_tls_eecdh_ultra;

 /*
  * Index to attach TLScontext pointers to SSL objects, so that they can be
  * accessed by call-back routines.
  */
int     TLScontext_index = -1;

 /*
  * Protocol name <=> mask conversion.
  */
static const NAME_CODE protocol_table[] = {
    SSL_TXT_SSLV2, TLS_PROTOCOL_SSLv2,
    SSL_TXT_SSLV3, TLS_PROTOCOL_SSLv3,
    SSL_TXT_TLSV1, TLS_PROTOCOL_TLSv1,
    0, TLS_PROTOCOL_INVALID,
};

 /*
  * Ciphersuite name <=> code conversion.
  */
const NAME_CODE tls_cipher_grade_table[] = {
    "high", TLS_CIPHER_HIGH,
    "medium", TLS_CIPHER_MEDIUM,
    "low", TLS_CIPHER_LOW,
    "export", TLS_CIPHER_EXPORT,
    "null", TLS_CIPHER_NULL,
    "invalid", TLS_CIPHER_NONE,
    0, TLS_CIPHER_NONE,
};

 /*
  * Parsed OpenSSL version number.
  */
typedef struct {
    int     major;
    int     minor;
    int     micro;
    int     patch;
    int     status;
} TLS_VINFO;

 /*
  * OpenSSL adopted the cipher selection patch, so we don't expect any more
  * broken ciphers other than AES and CAMELLIA.
  */
typedef struct {
    const char *ssl_name;
    const int alg_bits;
    const char *evp_name;
} cipher_probe_t;

static const cipher_probe_t cipher_probes[] = {
    "AES", 256, "AES-256-CBC",
    "CAMELLIA", 256, "CAMELLIA-256-CBC",
    0, 0, 0,
};

/* tls_exclude_missing - Append exclusions for missing ciphers */

static const char *tls_exclude_missing(SSL_CTX *ctx, VSTRING *buf)
{
    const char *myname = "tls_exclude_missing";
    static ARGV *exclude;               /* Cached */
    SSL    *s = 0;

    STACK_OF(SSL_CIPHER) * ciphers;
    SSL_CIPHER *c;
    const cipher_probe_t *probe;
    int     alg_bits;
    int     num;
    int     i;

    /*
     * Process a list of probes which specify:
     * 
     * An SSL cipher-suite name for a family of ciphers that use the same
     * symmetric algorithm at two or more key sizes, typically 128/256 bits.
     * 
     * The key size (typically 256) that OpenSSL fails to check, and assumes
     * available when another key size (typically 128) is usable.
     * 
     * The OpenSSL name of the symmetric algorithm associated with the SSL
     * cipher-suite. Typically, this is MUMBLE-256-CBC, where "MUMBLE" is the
     * name of the SSL cipher-suite that use the MUMBLE symmetric algorithm.
     * On systems that support the required encryption algorithm, the name is
     * listed in the output of "openssl list-cipher-algorithms".
     * 
     * When an encryption algorithm is not available at the given key size but
     * the corresponding OpenSSL cipher-suite contains ciphers that have have
     * this key size, the problem ciphers are explicitly disabled in Postfix.
     * The list is cached in the static "exclude" array.
     */
    if (exclude == 0) {
        exclude = argv_alloc(1);

        /*
         * Iterate over the probe list
         */
        for (probe = cipher_probes; probe->ssl_name; ++probe) {
            /* No exclusions if evp_name is a valid algorithm */
            if (EVP_get_cipherbyname(probe->evp_name))
                continue;

            /*
             * Sadly there is no SSL_CTX_get_ciphers() interface, so we are
             * forced to allocate and free an SSL object. Fatal error if we
             * can't allocate the SSL object.
             */
            ERR_clear_error();
            if (s == 0 && (s = SSL_new(ctx)) == 0) {
                tls_print_errors();
                msg_fatal("%s: error allocating SSL object", myname);
            }

            /*
             * Cipher is not supported by libcrypto, nothing to do if also
             * not supported by libssl. Flush the OpenSSL error stack.
             * 
             * XXX: There may be additional places in pre-existing code where
             * SSL errors are generated and ignored, that require a similar
             * "flush". Better yet, is to always flush before calls that run
             * tls_print_errors() on failure.
             * 
             * Contrary to documentation, on SunOS 5.10 SSL_set_cipher_list()
             * returns success with no ciphers selected, when this happens
             * SSL_get_ciphers() produces a stack with 0 elements!
             */
            if (SSL_set_cipher_list(s, probe->ssl_name) == 0
                || (ciphers = SSL_get_ciphers(s)) == 0
                || (num = sk_SSL_CIPHER_num(ciphers)) == 0) {
                ERR_clear_error();              /* flush any generated errors */
                continue;
            }
            for (i = 0; i < num; ++i) {
                c = sk_SSL_CIPHER_value(ciphers, i);
                (void) SSL_CIPHER_get_bits(c, &alg_bits);
                if (alg_bits == probe->alg_bits)
                    argv_add(exclude, SSL_CIPHER_get_name(c), ARGV_END);
            }
        }
        if (s != 0)
            SSL_free(s);
    }
    for (i = 0; i < exclude->argc; ++i)
        vstring_sprintf_append(buf, ":!%s", exclude->argv[i]);
    return (vstring_str(buf));
}

/* tls_apply_cipher_list - update SSL_CTX cipher list */

static const char *tls_apply_cipher_list(TLS_APPL_STATE *app_ctx,
                                         const char *context, VSTRING *spec)
{
    const char *new = tls_exclude_missing(app_ctx->ssl_ctx, spec);

    ERR_clear_error();
    if (SSL_CTX_set_cipher_list(app_ctx->ssl_ctx, new) == 0) {
        tls_print_errors();
        vstring_sprintf(app_ctx->why, "invalid %s cipher list: \"%s\"",
                        context, new);
        return (0);
    }
    return (new);
}

/* tls_protocol_mask - Bitmask of protocols to exclude */

int     tls_protocol_mask(const char *plist)
{
    char   *save;
    char   *tok;
    char   *cp;
    int     code;
    int     exclude = 0;
    int     include = 0;

    save = cp = mystrdup(plist);
    while ((tok = mystrtok(&cp, "\t\n\r ,:")) != 0) {
        if (*tok == '!')
            exclude |= code =
                name_code(protocol_table, NAME_CODE_FLAG_NONE, ++tok);
        else
            include |= code =
                name_code(protocol_table, NAME_CODE_FLAG_NONE, tok);
        if (code == TLS_PROTOCOL_INVALID)
            return TLS_PROTOCOL_INVALID;
    }
    myfree(save);

    /*
     * When the include list is empty, use only the explicit exclusions.
     * Otherwise, also exclude the complement of the include list from the
     * built-in list of known protocols. There is no way to exclude protocols
     * we don't know about at compile time, and this is unavoidable because
     * the OpenSSL API works with compile-time *exclusion* bit-masks.
     */
    return (include ? (exclude | (TLS_KNOWN_PROTOCOLS & ~include)) : exclude);
}

/* tls_param_init - Load TLS related config parameters */

void    tls_param_init(void)
{
    static const CONFIG_STR_TABLE str_table[] = {
        VAR_TLS_HIGH_CLIST, DEF_TLS_HIGH_CLIST, &var_tls_high_clist, 1, 0,
        VAR_TLS_MEDIUM_CLIST, DEF_TLS_MEDIUM_CLIST, &var_tls_medium_clist, 1, 0,
        VAR_TLS_LOW_CLIST, DEF_TLS_LOW_CLIST, &var_tls_low_clist, 1, 0,
        VAR_TLS_EXPORT_CLIST, DEF_TLS_EXPORT_CLIST, &var_tls_export_clist, 1, 0,
        VAR_TLS_NULL_CLIST, DEF_TLS_NULL_CLIST, &var_tls_null_clist, 1, 0,
        VAR_TLS_EECDH_STRONG, DEF_TLS_EECDH_STRONG, &var_tls_eecdh_strong, 1, 0,
        VAR_TLS_EECDH_ULTRA, DEF_TLS_EECDH_ULTRA, &var_tls_eecdh_ultra, 1, 0,
        0,
    };
    static const CONFIG_INT_TABLE int_table[] = {
        VAR_TLS_DAEMON_RAND_BYTES, DEF_TLS_DAEMON_RAND_BYTES, &var_tls_daemon_rand_bytes, 1, 0,
        0,
    };
    static int init_done;

    if (init_done)
        return;
    init_done = 1;

    get_mail_conf_str_table(str_table);
    get_mail_conf_int_table(int_table);
}

/* tls_set_ciphers - Set SSL context cipher list */

const char *tls_set_ciphers(TLS_APPL_STATE *app_ctx, const char *context,
                                  const char *grade, const char *exclusions)
{
    const char *myname = "tls_set_ciphers";
    static VSTRING *buf;
    int     new_grade;
    char   *save;
    char   *cp;
    char   *tok;
    const char *new_list;

    new_grade = tls_cipher_grade(grade);
    if (new_grade == TLS_CIPHER_NONE) {
        vstring_sprintf(app_ctx->why, "invalid %s cipher grade: \"%s\"",
                        context, grade);
        return (0);
    }
    if (buf == 0)
        buf = vstring_alloc(10);
    VSTRING_RESET(buf);

    /*
     * Given cached state and identical input, we return the same result.
     */
    if (app_ctx->cipher_list) {
        if (new_grade == app_ctx->cipher_grade
            && strcmp(app_ctx->cipher_exclusions, exclusions) == 0)
            return (app_ctx->cipher_list);

        /* Change required, flush cached state */
        app_ctx->cipher_grade = TLS_CIPHER_NONE;

        myfree(app_ctx->cipher_exclusions);
        app_ctx->cipher_exclusions = 0;

        myfree(app_ctx->cipher_list);
        app_ctx->cipher_list = 0;
    }
    switch (new_grade) {
    case TLS_CIPHER_HIGH:
        vstring_strcpy(buf, var_tls_high_clist);
        break;
    case TLS_CIPHER_MEDIUM:
        vstring_strcpy(buf, var_tls_medium_clist);
        break;
    case TLS_CIPHER_LOW:
        vstring_strcpy(buf, var_tls_low_clist);
        break;
    case TLS_CIPHER_EXPORT:
        vstring_strcpy(buf, var_tls_export_clist);
        break;
    case TLS_CIPHER_NULL:
        vstring_strcpy(buf, var_tls_null_clist);
        break;
    default:

        /*
         * The caller MUST provide a valid cipher grade
         */
        msg_panic("invalid %s cipher grade: %d", context, new_grade);
    }

    /*
     * The base lists for each grade can't be empty.
     */
    if (VSTRING_LEN(buf) == 0)
        msg_panic("%s: empty \"%s\" cipherlist", myname, grade);

    /*
     * Apply locally-specified exclusions.
     */
#define CIPHER_SEP "\t\n\r ,:"
    if (exclusions != 0) {
        cp = save = mystrdup(exclusions);
        while ((tok = mystrtok(&cp, CIPHER_SEP)) != 0) {

            /*
             * Can't exclude ciphers that start with modifiers.
             */
            if (strchr("!+-@", *tok)) {
                vstring_sprintf(app_ctx->why,
                                "invalid unary '!+-@' in %s cipher "
                                "exclusion: \"%s\"", context, tok);
                return (0);
            }
            vstring_sprintf_append(buf, ":!%s", tok);
        }
        myfree(save);
    }
    if ((new_list = tls_apply_cipher_list(app_ctx, context, buf)) == 0)
        return (0);

    /* Cache new state */
    app_ctx->cipher_grade = new_grade;
    app_ctx->cipher_exclusions = mystrdup(exclusions);

    return (app_ctx->cipher_list = mystrdup(new_list));
}

/* tls_alloc_app_context - allocate TLS application context */

TLS_APPL_STATE *tls_alloc_app_context(SSL_CTX *ssl_ctx)
{
    TLS_APPL_STATE *app_ctx;

    app_ctx = (TLS_APPL_STATE *) mymalloc(sizeof(*app_ctx));

    memset((char *) app_ctx, 0, sizeof(*app_ctx));
    app_ctx->ssl_ctx = ssl_ctx;

    /* See also: cache purging code in tls_set_ciphers(). */
    app_ctx->cipher_grade = TLS_CIPHER_NONE;
    app_ctx->cipher_exclusions = 0;
    app_ctx->cipher_list = 0;
    app_ctx->cache_type = 0;
    app_ctx->why = vstring_alloc(1);

    return (app_ctx);
}

/* tls_free_app_context - Free TLS application context */

void    tls_free_app_context(TLS_APPL_STATE *app_ctx)
{
    if (app_ctx->ssl_ctx)
        SSL_CTX_free(app_ctx->ssl_ctx);
    if (app_ctx->cache_type)
        myfree(app_ctx->cache_type);
    /* See also: cache purging code in tls_set_ciphers(). */
    if (app_ctx->cipher_exclusions)
        myfree(app_ctx->cipher_exclusions);
    if (app_ctx->cipher_list)
        myfree(app_ctx->cipher_list);
    if (app_ctx->why)
        vstring_free(app_ctx->why);
    myfree((char *) app_ctx);
}

/* tls_alloc_sess_context - allocate TLS session context */

TLS_SESS_STATE *tls_alloc_sess_context(int log_level, const char *namaddr)
{
    TLS_SESS_STATE *TLScontext;

    /*
     * PORTABILITY: Do not assume that null pointers are all-zero bits. Use
     * explicit assignments to initialize pointers.
     * 
     * See the C language FAQ item 5.17, or if you have time to burn,
     * http://www.google.com/search?q=zero+bit+null+pointer
     * 
     * However, it's OK to use memset() to zero integer values.
     */
    TLScontext = (TLS_SESS_STATE *) mymalloc(sizeof(TLS_SESS_STATE));
    memset((char *) TLScontext, 0, sizeof(*TLScontext));
    TLScontext->con = 0;
    TLScontext->internal_bio = 0;
    TLScontext->network_bio = 0;
    TLScontext->cache_type = 0;
    TLScontext->serverid = 0;
    TLScontext->peer_CN = 0;
    TLScontext->issuer_CN = 0;
    TLScontext->peer_fingerprint = 0;
    TLScontext->protocol = 0;
    TLScontext->cipher_name = 0;
    TLScontext->log_level = log_level;
    TLScontext->namaddr = lowercase(mystrdup(namaddr));

    return (TLScontext);
}

/* tls_free_context - deallocate TLScontext and members */

void    tls_free_context(TLS_SESS_STATE *TLScontext)
{

    /*
     * Free the SSL structure and the BIOs. Warning: the internal_bio is
     * connected to the SSL structure and is automatically freed with it. Do
     * not free it again (core dump)!! Only free the network_bio.
     */
    if (TLScontext->con != 0)
        SSL_free(TLScontext->con);
    if (TLScontext->network_bio)
        BIO_free(TLScontext->network_bio);

    if (TLScontext->namaddr)
        myfree(TLScontext->namaddr);
    if (TLScontext->serverid)
        myfree(TLScontext->serverid);

    if (TLScontext->peer_CN)
        myfree(TLScontext->peer_CN);
    if (TLScontext->issuer_CN)
        myfree(TLScontext->issuer_CN);
    if (TLScontext->peer_fingerprint)
        myfree(TLScontext->peer_fingerprint);

    myfree((char *) TLScontext);
}

/* tls_version_split - Split OpenSSL version number into major, minor, ... */

static void tls_version_split(long version, TLS_VINFO *info)
{

    /*
     * OPENSSL_VERSION_NUMBER(3):
     * 
     * OPENSSL_VERSION_NUMBER is a numeric release version identifier:
     * 
     * MMNNFFPPS: major minor fix patch status
     * 
     * The status nibble has one of the values 0 for development, 1 to e for
     * betas 1 to 14, and f for release. Parsed OpenSSL version number. for
     * example
     * 
     * 0x000906000 == 0.9.6 dev 0x000906023 == 0.9.6b beta 3 0x00090605f ==
     * 0.9.6e release
     * 
     * Versions prior to 0.9.3 have identifiers < 0x0930.  Versions between
     * 0.9.3 and 0.9.5 had a version identifier with this interpretation:
     * 
     * MMNNFFRBB major minor fix final beta/patch
     * 
     * for example
     * 
     * 0x000904100 == 0.9.4 release 0x000905000 == 0.9.5 dev
     * 
     * Version 0.9.5a had an interim interpretation that is like the current
     * one, except the patch level got the highest bit set, to keep continu-
     * ity.  The number was therefore 0x0090581f.
     */

    if (version < 0x0930) {
        info->status = 0;
        info->patch = version & 0x0f;
        version >>= 4;
        info->micro = version & 0x0f;
        version >>= 4;
        info->minor = version & 0x0f;
        version >>= 4;
        info->major = version & 0x0f;
    } else if (version < 0x00905800L) {
        info->patch = version & 0xff;
        version >>= 8;
        info->status = version & 0xf;
        version >>= 4;
        info->micro = version & 0xff;
        version >>= 8;
        info->minor = version & 0xff;
        version >>= 8;
        info->major = version & 0xff;
    } else {
        info->status = version & 0xf;
        version >>= 4;
        info->patch = version & 0xff;
        version >>= 8;
        info->micro = version & 0xff;
        version >>= 8;
        info->minor = version & 0xff;
        version >>= 8;
        info->major = version & 0xff;
        if (version < 0x00906000L)
            info->patch &= ~0x80;
    }
}

/* tls_check_version - Detect mismatch between headers and library. */

void    tls_check_version(void)
{
    TLS_VINFO hdr_info;
    TLS_VINFO lib_info;

    tls_version_split(OPENSSL_VERSION_NUMBER, &hdr_info);
    tls_version_split(SSLeay(), &lib_info);

    if (lib_info.major != hdr_info.major
        || lib_info.minor != hdr_info.minor
        || lib_info.micro != hdr_info.micro)
        msg_warn("run-time library vs. compile-time header version mismatch: "
             "OpenSSL %d.%d.%d may not be compatible with OpenSSL %d.%d.%d",
                 lib_info.major, lib_info.minor, lib_info.micro,
                 hdr_info.major, hdr_info.minor, hdr_info.micro);
}

/* tls_bug_bits - SSL bug compatibility bits for this OpenSSL version */

long    tls_bug_bits(void)
{
    long    bits = SSL_OP_ALL;          /* Work around all known bugs */

#if OPENSSL_VERSION_NUMBER >= 0x00908000L
    long    lib_version = SSLeay();

    /*
     * In OpenSSL 0.9.8[ab], enabling zlib compression breaks the padding bug
     * work-around, leading to false positives and failed connections. We may
     * not interoperate with systems with the bug, but this is better than
     * breaking on all 0.9.8[ab] systems that have zlib support enabled.
     */
    if (lib_version >= 0x00908000L && lib_version <= 0x0090802fL) {
        STACK_OF(SSL_COMP) * comp_methods;

        comp_methods = SSL_COMP_get_compression_methods();
        if (comp_methods != 0 && sk_SSL_COMP_num(comp_methods) > 0)
            bits &= ~SSL_OP_TLS_BLOCK_PADDING_BUG;
    }
#endif
    return (bits);
}

/* tls_print_errors - print and clear the error stack */

void    tls_print_errors(void)
{
    unsigned long err;
    char    buffer[1024];               /* XXX */
    const char *file;
    const char *data;
    int     line;
    int     flags;
    unsigned long thread;

    thread = CRYPTO_thread_id();
    while ((err = ERR_get_error_line_data(&file, &line, &data, &flags)) != 0) {
        ERR_error_string_n(err, buffer, sizeof(buffer));
        if (flags & ERR_TXT_STRING)
            msg_warn("TLS library problem: %lu:%s:%s:%d:%s:",
                     thread, buffer, file, line, data);
        else
            msg_warn("TLS library problem: %lu:%s:%s:%d:",
                     thread, buffer, file, line);
    }
}

/* tls_info_callback - callback for logging SSL events via Postfix */

void    tls_info_callback(const SSL *s, int where, int ret)
{
    char   *str;
    int     w;

    /* Adapted from OpenSSL apps/s_cb.c. */

    w = where & ~SSL_ST_MASK;

    if (w & SSL_ST_CONNECT)
        str = "SSL_connect";
    else if (w & SSL_ST_ACCEPT)
        str = "SSL_accept";
    else
        str = "unknown";

    if (where & SSL_CB_LOOP) {
        msg_info("%s:%s", str, SSL_state_string_long((SSL *) s));
    } else if (where & SSL_CB_ALERT) {
        str = (where & SSL_CB_READ) ? "read" : "write";
        if ((ret & 0xff) != SSL3_AD_CLOSE_NOTIFY)
            msg_info("SSL3 alert %s:%s:%s", str,
                     SSL_alert_type_string_long(ret),
                     SSL_alert_desc_string_long(ret));
    } else if (where & SSL_CB_EXIT) {
        if (ret == 0)
            msg_info("%s:failed in %s",
                     str, SSL_state_string_long((SSL *) s));
        else if (ret < 0) {
#ifndef LOG_NON_ERROR_STATES
            switch (SSL_get_error((SSL *) s, ret)) {
            case SSL_ERROR_WANT_READ:
            case SSL_ERROR_WANT_WRITE:
                /* Don't log non-error states. */
                break;
            default:
#endif
                msg_info("%s:error in %s",
                         str, SSL_state_string_long((SSL *) s));
#ifndef LOG_NON_ERROR_STATES
            }
#endif
        }
    }
}

 /*
  * taken from OpenSSL crypto/bio/b_dump.c.
  * 
  * Modified to save a lot of strcpy and strcat by Matti Aarnio.
  * 
  * Rewritten by Wietse to elimate fixed-size stack buffer, array index
  * multiplication and division, sprintf() and strcpy(), and lots of strlen()
  * calls. We could make it a little faster by using a fixed-size stack-based
  * buffer.
  * 
  * 200412 - use %lx to print pointers, after casting them to unsigned long.
  */

#define TRUNCATE_SPACE_NULL
#define DUMP_WIDTH      16
#define VERT_SPLIT      7

static void tls_dump_buffer(const unsigned char *start, int len)
{
    VSTRING *buf = vstring_alloc(100);
    const unsigned char *last = start + len - 1;
    const unsigned char *row;
    const unsigned char *col;
    int     ch;

#ifdef TRUNCATE_SPACE_NULL
    while (last >= start && (*last == ' ' || *last == 0))
        last--;
#endif

    for (row = start; row <= last; row += DUMP_WIDTH) {
        VSTRING_RESET(buf);
        vstring_sprintf(buf, "%04lx ", (unsigned long) (row - start));
        for (col = row; col < row + DUMP_WIDTH; col++) {
            if (col > last) {
                vstring_strcat(buf, "   ");
            } else {
                ch = *col;
                vstring_sprintf_append(buf, "%02x%c",
                                   ch, col - row == VERT_SPLIT ? '|' : ' ');
            }
        }
        VSTRING_ADDCH(buf, ' ');
        for (col = row; col < row + DUMP_WIDTH; col++) {
            if (col > last)
                break;
            ch = *col;
            if (!ISPRINT(ch))
                ch = '.';
            VSTRING_ADDCH(buf, ch);
            if (col - row == VERT_SPLIT)
                VSTRING_ADDCH(buf, ' ');
        }
        VSTRING_TERMINATE(buf);
        msg_info("%s", vstring_str(buf));
    }
#ifdef TRUNCATE_SPACE_NULL
    if ((last + 1) - start < len)
        msg_info("%04lx - <SPACES/NULLS>",
                 (unsigned long) ((last + 1) - start));
#endif
    vstring_free(buf);
}

/* taken from OpenSSL apps/s_cb.c */

long    tls_bio_dump_cb(BIO *bio, int cmd, const char *argp, int argi,
                                long unused_argl, long ret)
{
    if (cmd == (BIO_CB_READ | BIO_CB_RETURN)) {
        msg_info("read from %08lX [%08lX] (%d bytes => %ld (0x%lX))",
                 (unsigned long) bio, (unsigned long) argp, argi,
                 ret, (unsigned long) ret);
        tls_dump_buffer((unsigned char *) argp, (int) ret);
    } else if (cmd == (BIO_CB_WRITE | BIO_CB_RETURN)) {
        msg_info("write to %08lX [%08lX] (%d bytes => %ld (0x%lX))",
                 (unsigned long) bio, (unsigned long) argp, argi,
                 ret, (unsigned long) ret);
        tls_dump_buffer((unsigned char *) argp, (int) ret);
    }
    return (ret);
}

#else

 /*
  * Broken linker workaround.
  */
int     tls_dummy_for_broken_linkers;

#endif